When starting dbx:
$ dbx program-name process-ID
(dbx) debug program-name process-ID
If you include a - (minus sign) rather than a program name, dbx automatically finds the executable associated with the given process ID. After using a -, a subsequent run command or rerun command does not work because dbx does not know the full path name of the executable.
You can also attach to a running child process in the Oracle Developer StudioIDE. For more information, see the online help fro the IDE and for dbxtool.